The present invention relates to improvements in electrical switches, and in particular to a novel and rotary improved rotary switch of the type utilizing a cam for actuation of the switch mechanism.
In many rotary switch devices, particularly in rotary safety switches, the switching mechanism is opened and closed by a cam mounted on a shaft, with the cam rotating about the shaft, or rotating with the shaft. In either instance, the operative relationship between the cam surface and the switching mechanism is dependent, at least in part, upon the accuracy of location of the shaft, and the aperture in the cam through which the shaft passes.
In many rotary switch devices, particularly those in which safety functions are included, the accuracy and precise control of the switching mechanism is very important. The mere fact that a switch device operates may not be sufficient; it must operate at the same proper position with each actuation.
Conventional rotary switches normally require the provision and use of separate additional parts and components for mounting and guiding the cam in its rotary movement. Such parts may be shafts and related holes, special hubs built onto the cams to serve as centers of rotation, or the like. These parts are not directly related to the proper positioning of the cam during the switching operation and tend to create inaccuracies in the cam positioning. Further, the provision of additional parts or components increases the cost of producing the switch.
It is an object of the present invention to provide a switch having a rotary cam, in which the cam is rotatably mounted in a cavity formed in the switch housing, with the actual cam surface guided by said cavity. Thus, the necessity for using additional parts to mount and guide the cam is eliminated.
Another object of the invention is the provision of a switch of the character described in which the accuracy and dependability of the switching operation is appreciably improved, since accuracy of the dimensional relationship between the working surfaces results from utilizing the camming surface of the cam, in association with a correspondingly-shaped housing cavity, for guidance of the cam throughout its entire rotational movement.
Another object of the invention is the provision of a switch of the character described in which internal means are provided to limit the rotation travel of the cam to precise, preselected extreme positions, in close relationship to the operating positions of the switching mechanism. This insures that a precise relationship exists between the actuator cam and the switch mechanism so that the switch functions at the proper time and functions properly each time it is operated.
A further object of the invention is the provision of a switch of the character described in which the rotation limiting means comprises a pin and slot connection between the rotary cam and the switch housing, such pin and slot being formed integrally with the cam and housing, thereby eliminating the necessity for providing additional parts for this purpose.
A further object of the invention is the provision of a switch of the character described in which the rotation limiting means and its associated switch parts also serve as external indicating means by which the proper extreme positions of the switch, in its open and closed conditions, may be determined.